Western Hercules Beetle

Appearance

Adult body sizes of both sexes vary from 35 to 60mm , with captive-reared individuals reaching up to 80mm. Coloration of the elytra varies from white to grayish-white, often with irregular black spots of various size and number. At high humidity levels, the elytra may appear black.

''Dynastes grantii'' is sexually dimorphic, with the females lacking the characteristic horns of the male.

Naming

''Dynastes grantii'' belongs to the White Hercules beetle linage which includes five allopatrically distributed North American and Central American taxa, including ''Dynastes hyllus'', ''Dynastes maya, Dynastes moroni,'' and ''Dynastes tityus''. Despite differences in geographic origin and morphology, namely horn length and coloration of the elytra, ''Dynastes tityus'' and ''Dynastes grantii'' are very similar and it is possible for the two species to produce hybrids. Some scientists believe that the two beetles are actually subspecies given the similarities of the male genitalia.

''Dynastes grantii'' is very similar morphologically to ''Dynastes hyllus'', with differentiation between species often only possible through examination of geographic origin.

Distribution

Populations of ''Dynastes grantii'' may be found in southern Utah, Arizona, western New Mexico of the United States, and parts of Northern Mexico. This species typically inhabits highland forest habitats, at or above 1600m ASL.

Behavior

Like other hercules beetle species, ''Dynastes grantii'' undergoes a six-stage life cycle from egg to adult, with three larval instars and a single pupal stage. The time from egg to pupal eclosion is estimated to take approximately two years. The pupal stage lasts about 30 days. Adults emerge from the pupal chamber between the months of August through October and typically live between two and four months in the wild. In captivity, the adults may live up to nine months. After mating the female oviposits over 100 eggs.

Habitat

Populations of ''Dynastes grantii'' may be found in southern Utah, Arizona, western New Mexico of the United States, and parts of Northern Mexico. This species typically inhabits highland forest habitats, at or above 1600m ASL.

Food

Adults have been documented feeding on the cambium of ash trees. The beetles strip the bark from small branches and feed on the sap produced by the exposed cambium.